Gas-filled detectors have been used extensively in radiation detection and dosimetry. Such detectors have been used to measure various particles such as alpha-particles, neutrons, fission fragments, etc.; others have been used for measuring electromagnetic radiation, e.g., X- and gamma rays. In such detectors the ionizing radiation interacts with the counter gas to produce electrons, and ions by ionization, the electrons then being drawn to a collector at positive voltage thereby generating a signal that may be related to some characteristic (e.g., energy) of the radiation. Some of the desirable characteristics of the detector are: speed of electron collection which affects the time resolution and spatial resolution for position sensitive detectors, total charge transfer which affects the pulse height of the output signal, and energy resolution which affects identification of specific radiations.
In recent years the most commonly used filling gas for particle detectors is a 90% Ar-10% CH.sub.4 (methane) mixture which is designated as P-10. The most common counter gases for electromagnetic radiation are 90% Xe-10% CH.sub.4 or b 90% Xe-10% CO.sub.2. Currently, these gases are standards against which other gases are evaluated. However, these gases have certain deficiencies. For example, the electron drift velocities are high over only a very narrow E/P (pressure-reduced electric field) range thus putting constraints on the pressure and the collection voltage, and the maximum drift velocities are limiting for some applications.
Thus, there exists a need for providing improved and more efficient gas mixtures for gas-filled radiation detectors. The present invention was conceived to meet this need in a manner to be described hereinbelow.